We derive the finite-temperature unconditional master equation of density matrix for two coupled quantum dots (CQD) when one dot is subjected to a measurement of its electron occupation number using a quantum point contact (QPC). By tracing out the thermal QPC reservoir degrees of freedom, we obtain the temperature dependent decoherence rate. To know how the CQD system state depends on the actual current through the QPC device, we use the so-called quantum trajectory method to derive the zero-temperature conditional master equation. We first treat the electron tunneling through the QPC barrier as a classical stochastic point process (a quantum jump model). Then we show explicitly that our results can be extended to the quantum diffusive limit when the average electron tunneling rate is very large compared to the extra change of the tunneling rate due to the presence of the electron in the dot closer to the QPC. We find that in both quantum jump and quantum diffusive cases, the conditional dynamics of the CQD system can be described by the stochastic Schr\"{o}dinger equations for its conditioned state vector if and only if the information carried away from the CQD system by the QPC reservoirs can be recovered by the perfect detection of the measurements.